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/cvs/libecb/ecb.h
Revision: 1.3
Committed: Thu May 26 16:57:04 2011 UTC (13 years ago) by root
Content type: text/plain
Branch: MAIN
Changes since 1.2: +29 -12 lines
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File Contents

# Content
1 /*
2 * libecb
3 *
4 * Copyright (©) 2009-2011 Marc Alexander Lehmann
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without modifica-
8 * tion, are permitted provided that the following conditions are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright notice,
11 * this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26 * OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #ifndef ECB_H
30 #define ECB_H
31
32 #define ECB_GCC_VERSION(major,minor) (__GNUC__ > (major) || (__GNUC__ == (major) && __GNUC_MINOR__ >= (minor)))
33
34 #define ECB_HEADER_INLINE static inline
35
36 #if ECB_GCC_VERSION(3,1)
37 # define ecb_attribute(attrlist) __attribute__(attrlist)
38 # define ecb_is_constant(c) __builtin_constant_p (c)
39 # define ecb_expect(expr,value) __builtin_expect ((expr),(value))
40 # define ecb_prefetch(addr,rw,locality) __builtin_prefetch (addr, rw, locality)
41 #else
42 # define ecb_attribute(attrlist)
43 # define ecb_is_constant(c) 0
44 # define ecb_expect(expr,value) (expr)
45 # define ecb_prefetch(addr,rw,locality)
46 #endif
47
48 /* no emulation for ecb_decltype */
49 #if ECB_GCC_VERSION(4,5)
50 # define ecb_decltype(x) __decltype(x)
51 #elif ECB_GCC_VERSION(3,0)
52 # define ecb_decltype(x) typeof(x)
53 #endif
54
55 #define ecb_noinline ecb_attribute ((noinline))
56 #define ecb_noreturn ecb_attribute ((noreturn))
57 #define ecb_unused ecb_attribute ((unused))
58 #define ecb_const ecb_attribute ((const))
59 #define ecb_pure ecb_attribute ((pure))
60 #define ecb_hot ecb_attribute ((hot)) // 4.3
61 #define ecb_cold ecb_attribute ((cold)) // 4.3
62
63 #if ECB_GCC_VERSION(4,5)
64 # define ecb_unreachable() __builtin_unreachable ()
65 #else
66 /* this seems to work fine, but gcc always emits a warning for it :/ */
67 ECB_HEADER_INLINE void ecb_unreachable () ecb_attribute ((noreturn));
68 ECB_HEADER_INLINE void ecb_unreachable () { }
69 #endif
70
71 /* put into ifs if you are very sure that the expression */
72 /* is mostly true or mosty false. note that these return */
73 /* booleans, not the expression. */
74 #define ecb_expect_false(expr) ecb_expect ((expr) ? 1 : 0, 0)
75 #define ecb_expect_true(expr) ecb_expect ((expr) ? 1 : 0, 1)
76
77 /* try to tell the compiler that some condition is definitely true */
78 #define ecb_assume(cond) do { if (!(cond)) unreachable (); } while (0)
79
80 /* count trailing zero bits and count # of one bits */
81 #if ECB_GCC_VERSION(3,4)
82 ECB_HEADER_INLINE int ecb_ctz (unsigned int x) { return __builtin_ctz (x); }
83 ECB_HEADER_INLINE int ecb_popcount (unsigned int x) { return __builtin_popcount (x); }
84 #else
85 ECB_HEADER_INLINE
86 ecb_ctz (unsigned int x) ecb_const
87 {
88 int r = 0;
89
90 x &= -x; // this isolates the lowest bit
91
92 if (x & 0xaaaaaaaa) r += 1;
93 if (x & 0xcccccccc) r += 2;
94 if (x & 0xf0f0f0f0) r += 4;
95 if (x & 0xff00ff00) r += 8;
96 if (x & 0xffff0000) r += 16;
97
98 return r;
99 }
100
101 ECB_HEADER_INLINE
102 ecb_popcount (unsigned int x) ecb_const
103 {
104 x -= (x >> 1) & 0x55555555;
105 x = ((x >> 2) & 0x33333333) + (x & 0x33333333);
106 x = ((x >> 4) + x) & 0x0f0f0f0f;
107 x *= 0x01010101;
108
109 return x >> 24;
110 }
111 #endif
112
113 ECB_HEADER_INLINE unsigned char
114 ecb_byteorder_helper () ecb_const
115 {
116 const uint32_t u = 0x11223344;
117 return *(unsigned char *)&u;
118 }
119
120 ECB_HEADER_INLINE bool ecb_big_endian () ecb_const { return ecb_byteorder_helper () == 0x11; };
121 ECB_HEADER_INLINE bool ecb_network () ecb_const { return big_endian (); };
122 ECB_HEADER_INLINE bool ecb_little_endian () ecb_const { return ecb_byteorder_helper () == 0x44; };
123 ECB_HEADER_INLINE bool ecb_vax () ecb_const { return little_endian (); };
124
125
126 #endif
127